Gas compressing apparatus



P 1950 H. R. RICARDO E'I'AL 2,522,638

GAS COMPRESSING APPARATUS Filed June 13, 1945' 4 Sheets-Sheet 1 L F/G.

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(1,6 M \r m A ttorney pt 19, 1950 H. R. RICARDO EIAL 2,522,638

GAS COMPRESSING APPARATUS- Filed June 13, 1945 4Sheets-Sheet 2 AttorneySept. 19, 1950 I H. R. RICARDO ETAL 2,522,538

GAS COMPRESSING APPARATUS Filed June 13, 1945 4 Sheets-Sheet 3 4 BI 55 AD A3 Sept. 19, 1950 H. R. RICARDO EIAL 2,522,633

GAS COMPRESSING APPARATUS Filed June 13, 1945 4 Sheets-Sheet 4lllllllllllllllllllmm Patented Sept. 19, 1950 GAS COMPRESSING APPARATUSHarry Ralph Ricardo,

Thomas Evans, Worthing, England; said Evans assignor to said RicardoApplication June 13, 1945, Serial No. 599,268 In Great Britain May 3,1944 4 Claims.

This invention relates to gas compressing apparatus adapted moreparticularly for ,use in the compression of oxygen and has for itsobject to provide a compressing plant and also an improved constructionof compressor to be used therein, the compressor being of the type inwhich water for the purpose of lubricating the pistons is admitted withthe gas to be compressed.

In known oxygen compressing apparatus in which compressors of this typeare used the separation of the water supplied for lubrication of thecylinders from the gas after compression has been effected in aseparator constructed and arranged so that the accumulated water must beremoved therefrom periodically and passed into a separate waterreservoir or allowed to run to waste. This procedure is avoided in thepresent improved plant which is compact, simple in construction andcapable of continuous automatic operation in that there is no need forthe intermittent evacuation of accumulated water.

According to this invention in the improved compressing apparatus thewater following a closed circuit enters the cylinders with the gas to becompressed and leaves these cylinders with the compressed gas passingthence through a cooler to a gas and water reservoir from which thewater flows back to re-enter the cylinders with the incoming gas. Thewater used in this circuit flows to the cylinders through a meteringdevice and is in such quantity as to abstract substantially all the heatof compression and friction while also lubricating the cylinders so thatall the cooling necessary is effected internally and as the water passeswith the gas through the cylinders. The metering device is constitutedby a fixed resistance in the path of the water flowing in the closedcircuit from the gas and water reservoir to the cylinders and takes theform of a length of capillary tube through which the water has to pass.

The path of the gas through the apparatus and the circuit followed bythe water as it is used in the compressor comprise the followingfeatures, the compressor having for example two stages. The gas is drawninto the cylinder of the first stage and with it enters the water as itissues under pressure from the capillary tube metering device. The gasand water pass from this low pressure cylinder into the cylinder of thesecond stage and are delivered together thence through a cooler into thegas and water reservoir. The gas from this reservoir is led through adrier and then taken for storage or use. The water, under the pressurein the reservoir can flow con- London, and Aubrey tinuously through afilter to the metering device from which is issues to again enter thecylinder of the first stage with the fresh supply of gas. Means areprovided for shutting off the gas delivery from the drier and leadingthe gas by a short-circuiting pipe back to the supply pipe, an.arrangement which is of use when it is desired to change a fully chargedstorage cylinder for an empty or partially empty one.

The accompanying drawings illustrate by way of example a compressorconstructed according to this invention and the circuit in which thiscompressor is intended to be used. In these drawings:

Figure 1 is a vertical sectional elevation of a two-stage compressor. v

Figure 215 a similar view showing the cylinders of the first and secondstages on a somewhat larger scale.

Figure 3 is a section through the cylinder of the first stage on theline 3-3 in Figure 2 looking in the direction of the arrows.

Figure 4 is a transverse section through the first and second stagecylinders the section being on the line 4-4 in Figure 3.

Figure 5 is a vertical sectional elevation through the high pressurev orsecond stage cylinder the section being mainly on the line 5-5 in Figure4, but as to the part of the first stage cylinder which appears inFigure 5 the section is on the line 5a-5a in Figure 4.

Figure 6 is a longitudinal sectional elevation of the end of the secondstage or high pressure cylinder showing an alternative arrangement ofthe delivery valve at the end of the cylinder.

Figure 7 is a longitudinal section through the water supply pipe showingan arrangement of the capillary tube which functions as a meteringdevice.

Figure 8 is a diagrammatic representation of the compressing apparatus.

As mentioned the compressor here more particularly described by way ofexample is a twostage one having the first stage or low pressurecylinder'A and the second stage or high pressure cylinder B. The pistonC which is shown as of the trunk type in the low pressure cylinder A andthe piston D of the plunger type in the high pressure cylinder B arerespectively connected to the crank shaft E which is driven from somesuitable source of power. A rod C couples the piston C to one end of aguide member C from whose other end a connecting rod C runs to a crankon the shaft E, the guide member C reciprocating in what is in effect acrosshead guide Ihe plunger D is directly connected to one end of asimilar guide member I) at the other end or which is a connecting rod Dextending to the crank shaft, the guide member D reciproeating in aguide D. In a cylinder A is a liner A in the wall of which are the inletports A leading from an annular space or inlet belt A into which the gasand water enter from the lateral chamber F. Delivery of the gas andwater is through the end of the cylinder where is a nonreturn valveconstituted by a disc G which is acted on by a spring G and is seated onthe end of the liner A Delivery past the valve G is through the passageA seen in Figure 5, to the high pressure cylinder B. In some cases theinlet ports A may lead tangentially into the cylinder A. The piston Ccarries no packing device reliance being placed on the relatively closefit of the long trunk in the liner A and the packing effect of thewater.

In the high pressure cylinder B is a liner B in the wall of which arethe inlet ports 13 leading from the annular space or inlet belt B intowhich runs the passage B communicating, asseen in Figure 5, with thedelivery passage A from the low pressure cylinder A. The gas and waterare delivered through the end of the cylinder B past the non-return discvalve H to the pipe B which leads ofi laterally. The valve H on whichacts the spring H is seated on a ring H which in turn rests on the endof the liner B When the seating of the valve H on the ring H becomesworn this arrangement enables the seating to be renewed by inserting anew ring thus avoiding the need for removing the liner B as might benecessary if the valve was seated directly on the end of the liner; italso allows the seating to be made in a material difierent from that ofwhich the liner is made.

The valve H may be variously arranged, two alternative constructionsbeing shown in Figures 5 and 6. In that seen in Figure 5, which is alsoshown in Figures 1 and 2, the valve disc H is formed on the end of asleeve H which is guided in a cylindrical member H fixed in the end ofthe cylinder B beyond the end of the liner B The spring H which tends tokeep the valve disc H on its seat on the ring 1-1 is guided by a centralpin H which also acts as a stop to limit the lift of the valve and atits end abuts against a shoulder on this pin. In the alternativearrangement shown in Figure 6, the valve disc H is not guided, butfloats freely except for the spring H which bears against the back ofthe disc with its other end abutting against a plug H fixed in the endof the cylinder B.-

The manner in which the capillary tube, which serves as a meteringdevice for the water, is arranged is shown in Figure 7. This tube J nearone end passes through and is held by a plug J which is fixed in the endJ of the pipe J through which the water flows under pressure to thechamber F into the side of which projects the end of the tube J. Asuitable length of the capillary tube lies within the pipe J where it issubjected externally as well as internally to the high pressure at whichthe water is supplied. Such a length of capillary tubing, which forexample may be made from stainless steel, will satisfactorily resisterosion and corrosion when employed in the delivery and for the purposeof metering highly oxygenated water passing through the tubing at highvelocity for use in an oxygen compressor.

Diiierence oi. pressure lbs. Flow in per sq inch gallons gauge betweenper hour ends of pipe 0 0 500 6 l, 000 9. 5 l, 500 ll. 5 2,000 13.5 2,500 15. 5 3, 000 17. 5 3, 500 19. 3

This tube will satisfactorily control the flow of highly oxygenatedwater in an oxygen compressor of a determined size and constructed asabove described. The tube may be arranged in various ways as foundconvenient, but in each case the water will be delivered through it at asubstantially constant rate for a constant pressure difference into thechamber F while the compressor is being driven at a fixed speed. Thewater is drawn from the chamber through the ports A into the cylinder Awith the gas from the source of supply which enters the chamber Fthrough the piping L and as described the gas and water then passtogether through the compressor cylinders. It will be perceived thattube J constitutes a fixed; low velocity, distributed resistance to thefiow of water, the term distributed resistance" being employedhereinafter to designate a resistance eflective at a plurality of pointsspaced substantially in the direction of flow. The use of such aresistance is of outstanding importance in the practice of theinvention, owing to the high pressures employed in oxygen compressorsand the like. At such pressures, the metering of the water by the use ofa conventional orifice is wholly impractical, the size of orificerequired being so .small that choking with fine particles, as well asrapid erosion, is inevitable. These defects are overcome by distributingthe resistance to flow over a substantial length of the supply conduit,whereby the desired total resistance may be achieved without unfavorably10w dimensioning of the passage.

Suitable stufling glands or other devices may be provided to preventlubricating oil from working past the crosshead guides C D towards theglands of the compressing cylinders A and B. The cylinder liners areformed of bronze and .preferably in the case of the high pressure linerof chromium bronze and the piston C and plunger D of stainless steelchromium plated. As mentioned each piston or plunger carries no packingdevice but relies for gas-tightness on the water and the close fit ofthe piston in its'liner. A suitable clearance is 0.001 inch for a lowpressure piston of 2 inch diameter and 0.0005 inch for a high pressureplunger of inch-diameter. At the outer end of the liner A is a stufllnggland A through which runs the trunk of the piston C. In the case of thehigh pressure cylinder B there is a similar gland B, but it isconvenient to provide some means whereby water and gas which may leakpast the plunger D may be trapped and dealt with. For this purpose, andas an example, a lantern B may be provided between the outer end of theliner B and the gland packing B and from the trap thus formed any gasand water which finds its way along the plunger D will be returnedthrough the passage B to the inlet belt A around the liner A of the lowpressure cylinder and so to the inlet ports A. In this way these glandsmay be subjected only to the inlet pressure of the first stage.

Since in each stage'the inlet ports in the wall of the cylinder linerare spaced from the inner or high pressure end of the cylinder byadistance representing a substantial portion of the stroke of the pistonat the time of maximum pressure, a long seal is provided and any gas orwater which may find its way along the surface of the plunger isreceived into the inlet ports. Hence in the second stage the contactingportion of the plunger D and liner B beyond the inlet ports B" andtowards the stufiing gland B can be subjected only to a pressuredifference represented by the interstage pressure and the inlet pressureto the first stage.

It may be noted that by constructing and arranging the automaticdischarge valves G and If so that each forms in effect the whole end, ofits cylinder it becomes impossible for a lock-up of water to occur inthe cylinders A and B and the end of each piston can be brought close tothe face of the valve in the end of the cylinder at the end of thein-stroke. This arrangement in combination with the water which will bepresent on the face of the plunger reduces the clearance losses to anegligible amount.

It is desirable to provide a safety or relief valve M in the passage A Bbetween the low and high pressure cylinders. This avoids any risk atstarting-up of a lock-up with any water between the delivery A from thelow pressure cylinder A and the inlet to the high pressure cylinder Bwhich may have leaked past the water metering device while thecompressor is standing still with the reservoir under pressure.

Turning now to Figure 8 this shows diagrammatically the generalarrangement of the improved compressing plant in a form which isparticularly suitable for use in transferring oxygen from a partiallyempty storage cylinder and compressing the oxygen into an empty orpartially empty storage cylinder. In the gas supply pipe L there is anon-return valve L and a reducing valve L and through this pipe and thewater supply pipe J wherein is the metering device. gas and water fiowto the inlet belt A of the low pressure cylinder A. The gas and waterare delivered past the valve G on the instroke of the piston or plungerC and pass through the passage A B to the inlet belt B and through theports into the high pressure cylinder B. As mentioned a safety valve Mis arranged in the passage A B and there is an additional reason forthis beyond its function as indicated above. The quantity of waterdelivered by the capillary metering device J in unit time is dependenton the pressure existing in the water supply pipe J whereas the capacityof the compressor to receive water is determined by the volumedisplacement of the second stage Plunger D in unit time. Therefore ifthe rotational speed of the compressor should fall appreciably below thespeed assumed when determining the proportions of the capillary tube Jfor a given reservoir pressure, then more water may be fed into thecompressor than the displacement of the second stage can accommodate.

The gas and water delivered from the high pressure cylinder B past thevalve H is led by the pipe I? through a cooler N which may be some knownform of heat exchange apparatus, or in some cases may be constituted bya cooling Jacket surrounding the pipe B Thence the gas and water enterthe reservoir 0 wherein they separate, the water collecting in'the lowerpart of the reservoir the form of which is preferably such that itsheight is materially greater than its diameter. The reservoir may beprovided with a safety valve 0 From the bottom of the reservoir, thewater, under the pressure existent in the reservoir, is taken back by apipe J to a filter J whence it flows once more through the pipe J andthe metering capillary tube J to enter the low pressure cylinder A witha fresh supply of gas.

In those cases in which it is desirable that the compressed gas shall bedelivered from the reservoir O in a reasonably dry state the gas leavingthe reservoir through the pipe P is taken to a drying device Q such as asilica-gel drier. In the pipe P is a spring-loaded valve P so that whenin operation a, pressure of a predetermined minimum value, for instancenot less than 200 lbs. per square inch, will be maintained in thereservoir to ensure that a sufficient amount of water is supplied to thecompressor to maintain the compressor at a safe temperature at normalspeed. There is a valve P in a branch from the pipe P to enable the gaspressure to be blown down before stopping the compressor so that thesupply of water to the compressor may cease when the compressor isstopped. The gas is led off from the drier through the pipe R in whichis a valve R Between this valve and the drier a pipe R in which is avalve R runs back into the gas supply pipe L entering that pipe betweenthe non-return valve L and the reducing valve L There is a valve P inthe pipe P between the spring-loaded valve P and the drier Q. If beforestopping the compressor the valves P and R are shut the silica-gel inthe drier Q will be locked up under the maximum pressure existing in theplant before it is stopped.

A compressor plant as described above may be used in various ways. Forexample it may be employed as a transfer pump to take the contents ofpartly filled storage vessels and transfer the gas from them at highpressure to another partly filled storage vessel, or it may be used toreceive gas at a low or at atmospheric pressure and pump the gas into astorage vessel at a high pressure. In the latter case the reducing valveL is conveniently removed from the position in which it is shown in thepipe L and placed in the pipe R because reducing valves suitable toreceive gas at high pressure will not function if fed with gas at verylow or at atmospheric pressure. By moving the reducing valve to aposition in the pipe R low pressure gas can pass to the first stageinlet while any gas by-passed through the pipe R will be reduced inpressure before passing to the first stage inlet for re-circulation.

When using the apparatus as a transfer pump the procedure at starting isas follows. Before starting up, the quantity of water in the system ischecked and if necessary more Water is added to the reservoir through afilling plug provided in the top of the reservoir. The vessel in whichthe gas is to be stored is connected to the pipe R and its valve isopened. One or more partly empty vessels from which the gas is to betaken are connected to the pipe L. The valves P R P and R are all closedand the valves of the partly empty vessels are opened. The compressor,driven conveniently by an electric motor, is then started up and quicklybrought to its normal running speed, As it continues running thepressure in the reservoir will rise and when this pressure reaches avalue equal to or slightly higher than the pressure in the vesselconnected to the delivery pipe R the valves P and R are opened. When thedesired maximum pressure has been reached in the vessel into which thegas is being transferred, or when the pressure in the vessels from whichit is being removed has fallen to the permissible minimum, the plantmust be unloaded so that the vessels to which it is connected may beremoved and others substituted for them. To unload the plant the valve Ris first shut and the valve R is then opened. This allows the gasleaving the drier Q to flow back through the pipe R to the inlet pipe L.Owing to the non-return valve L the gas cannot flow back and escapethrough the supply pipe L, and the reducing valve L whether this is inthe pipe L or in the return pipe R ensures that the pressure of the gasflowing back in the pipe R will be brought down to a suitable valuebefore the gas enters the inlet belt A of the low pressure cylinder onits way to being again circulated in the plant. When the plant is to bestopped, the valves R 1 and R. are closed thereby shutting 01! deliverythrough the pipes P and R and R. and thus locking up the pressure in thedrier Q, and the blow-down valve P is opened. When the pressure in thereservoir 0 has fallen to a low value the compressor can be stopped.

Owing to the internal cooling of the plant which is effected by thepassage through the cylinders of a sufllcient quantity of water toperform the cooling and the subsequent cooling of this water before itagain passes through the cy1-. inders, the need for performing externalcooling, as by arranging a water jacket or radiating fins or the like onthe outside of the cylinder block, is obviated.

It is to be understood that while it is convenient to use a compressorcomprising the features indicated above and described hereunder more in.detail, the improved gas compressing apparatus may be operated with theclosed water circuit and automatic internal cooling by employing someother construction of compressor. The present construction, however,provides an effective plant especially suitable for the compression ofoxygen. v

What we claim as our invention and desire to secure by Letters Patentis:

1. Gas compressing apparatus comprising in combination at least twocylinders with pistons therein which are reciprocated from a source ofpower and constituting a multi-stage compressor,

means for delivering water in measured quantity with the gas enteringthe cylinder of the first stage of the said compressor, a cooler throughwhich passes the compressed gas leaving the cylinder of the last stageand also water which is carried over with the gas this v water havingserved to lubricate the pistons in the cylinders of the said compressorand also to abstract substantially all the heat of compression andfriction, a reservoir in which the gas and water accumulate afterpassing through the cooler and whence the compressed gas is taken foruse, and a pipe through which the water in the reservoir is taken to ametering device comprising a fixed low velocity distributed resistancethrough which it passes and is again taken into the cylinder of thefirst stage of the said compressor with the gas so that this watercontinuously follows a closed circuit.

2. Gas compressing apparatus comprising in combination the features setout in claim 1 and in which the close fitting surfaces in contact ofeach piston and rod and plunger in the cylinders of the said compressorare sealed solely by the water passing through the cylinders no packingbeing provided.

3. Gas compressing apparatus comprising in combination the features asset out in claim 1 and in which in the said pipingthrough which thewater is conveyed from the said reservoir back to the cylinder of thefirst stage of the said compressor there is fixed a length of capillarytube through which the water has to pass and which acts as a fixeddistributed resistance metering device for the water taken into thefirst stage of the compressor with the gas.

4. In gas compressing apparatus, the combination with amulti-stagecompressor, each stage comprising a cylinder having a piston therein,and driving means for reciprocating said pistons, 01 devices deliveringwater in measured quantity with the gas entering the first stagecylinder, a cooler. means delivering the compressed gas and entrainedwater from the last stagepylinder to said cooler, and a reservoirreceiving the cooled gas and water from said cooler, said devicesreceiving water from said reservoir and including a capillary tube.constitutin a, fixed low velocity distributed resistance by which thewater returned to said first stage cylinder is metered.

HARRY RALPH RICARDO. AUBREY THOMAS EVANS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

